JP3776738B2 - Switching signal generator - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to a switching signal generator in which a switching signal of a power switch element is fed back from a gate driver circuit output to a modulator in a switching power supply using a ΔΣ modulator.
[0002]
[Prior art]
A conventional PWM (pulse modulation) switching signal generator modulates an input signal by changing a pulse width. That is, as shown in the block diagram of the PWM switching signal generator in FIG. 2, a gate signal can be generated from the input signal 1 by the PWM oscillator 18, and the signal can be amplified by the gate driver circuit 6 to drive the power switch element 7. However, in the PWM method, the distortion generated in the gate driver circuit 6 cannot be corrected.
[0003]
A block diagram in which a conventional PWM switching signal generator is applied to a step-down chopper is shown in FIG. Although the voltage applied to the load is compared with the reference voltage 17 and input to the PWM oscillator 18 and the power switch element 7 is controlled by the output of the PWM oscillator 18, it does not have a direct feedback path from the gate driver circuit 6. Therefore, it is impossible to directly correct the distortion generated in the gate driver circuit 6.
[0004]
Further, as shown in FIG. 3, instead of the PWM oscillator, an input signal is integrated by an integrator 3 and a gate drive signal is applied to the power switch element 7 by using a delta-sigma modulator 5 which quantizes the input signal into a 1-bit output signal. Although it is possible to provide a switching signal generator that drives the power switch element 7 by outputting, it is impossible to correct the distortion generated in the gate driver circuit 6 because feedback is performed before the gate driver input.
[0005]
FIG. 7 shows a block diagram in which a conventional ΔΣ switching signal generator is applied to a step-down chopper. In this method, the voltage applied to the load and the reference voltage 17 are compared and input to the ΔΣ modulator 5, and the power switch element 7 is controlled by the output of the ΔΣ modulator 5, but it has a direct feedback path from the gate driver circuit 6. Therefore, it is impossible to directly correct the distortion generated in the gate driver circuit 6.
[0006]
As a result, the distortion of the gate driver circuit 6 that directly drives the power switch element 7 cannot be removed, and the linearity of the ΔΣ modulator is deteriorated.
[0007]
Due to distortion generated in the gate driver circuit in both the PWM method and the conventional ΔΣ method, an error occurs between the PWM oscillator output signal in the PWM method and the output signal of the ΔΣ modulator and the gate driver output signal in the conventional ΔΣ method. When used as a control, particularly when operated at a high frequency, the phase margin is small and the control becomes unstable.
[0008]
In addition, a phase correction circuit will be added to prevent oscillation, but the number of parts will increase and the cost will increase. In addition, in order to design an optimal circuit, experiment and confirmation will be performed using an actual circuit. In many cases, stable circuit design is difficult and the development time is increased.
[0009]
In addition, there is a method for improving linearity by inputting an analog signal and feeding back an output signal of a power switch element like a switching amplifier using ΔΣ modulation as disclosed in Japanese Patent Laid-Open No. 2000-307359.
[0010]
FIG. 5 shows a conventional ΔΣ modulation system that feeds back the output signal of the power switch element, and FIG. 5 is a block diagram thereof. However, when this conventional method is used for switching power supply control, there are the following problems. It was.
[0011]
When the output current of the switching power supply is small, there is a discontinuous region where the current flowing through the inductance in the power supply circuit becomes discontinuous. When the current flowing through the inductance becomes 0 in this discontinuous region, oscillation occurs due to the capacitance component and the inductance component in the power supply circuit.
[0012]
As shown in FIG. 5, in the method of feeding back the power switch element output signal to the ΔΣ modulator, noise due to this oscillation is also fed back, the number of times of switching of the ΔΣ modulation output is remarkably increased, and as a result, the switching loss is increased. There was a problem of reducing efficiency.
[0013]
That is, in the conventional switching signal generation method, since the distortion generated in the gate driver is difficult to remove, the linearity of the DC transmission characteristic is poor, and the linearity is not good, so that the phase margin is small and the oscillation phenomenon easily occurs.
[0014]
In addition, in the method using ΔΣ modulation having a feedback path from the latter stage of the power switch element in order to improve the linearity, there is a problem that the power supply efficiency is lowered due to noise at the time of current discontinuity.
[0015]
[Problems to be solved by the invention]
In a switching power supply using a ΔΣ modulator, a switching signal generator capable of stable control by high frequency switching with high efficiency and large phase margin is provided.
[0016]
[Means to solve the problem]
In order to achieve the above object, the invention described in the claims is that an analog input signal or a multi-bit digital signal is input to a delta-sigma modulator, the modulation signal is amplified by a gate driver circuit, and the power switch element is used by the signal In the switching power supply to be switched, the gate driver output is fed back to the ΔΣ modulator.
[0017]
The ΔΣ modulator is composed of at least one adder, integrator, and quantizer, and has a feedback path from the gate driver circuit output connected to the quantizer output to at least one adder input. An integrator is connected to the output of the adder, and at least one of the integrator outputs is connected to the quantizer.
[0018]
The adder that is the input to the delta-sigma modulator and the integrator connected to the output of the adder use an analog adder and an analog integrator when a continuous time signal such as an analog signal is input to the modulator. When a discrete time signal such as a multi-bit digital signal is input to the modulator, a digital adder and a digital integrator can be used.
[0019]
The quantizer is a quantizer that samples a discrete-time signal and is connected to the input of a gate driver circuit that receives the output signal of the quantizer and supplies current and voltage sufficient to drive the power switch element. .
[0020]
The feedback path includes an attenuator that adapts the large amplitude pulse signal of the gate driver circuit to the ΔΣ modulator input signal level. However, it goes without saying that an attenuator with an attenuation factor of 0 is included even when the gate driver circuit output level and that of the ΔΣ modulator input are adapted from the beginning and no attenuator is required.
[0021]
Since there is a feedback path from the gate driver output connected to the quantizer output to the modulator input, distortion generated by the gate driver is reduced, and the conventional PWM system and the ΔΣ modulator that feeds back immediately after the conventional quantizer Compared with, the distortion generated in the gate driver can be directly fed back.
[0022]
Further, since the gate driver circuit output connected to the quantizer output is directly fed back to the modulator input, the linearity of the input / output characteristics is good, the phase margin is large, and oscillation does not easily occur.
[0023]
By directly feeding back from the gate driver output, the distortion generated in the gate driver circuit can be fed back directly, and when switching to a switching power supply with less noise than when feeding back in the subsequent stage of the power switch element, switching loss is reduced. Can do.
[0024]
Although it is clear that the output is amplified to DC power by converting the analog input signal to DC voltage, it can clearly function as a DC switching power supply. However, a rectification smoothing circuit is inserted after the power switch element, and a ΔΣ modulation type chopper It can also be configured as a power source.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a switching signal generator according to the present invention will be described below with reference to the accompanying drawings. In the description of the drawings, the same members are denoted by the same reference numerals, and redundant descriptions are omitted.
[0026]
FIG. 1 shows an embodiment of the present invention, and FIG. 1 is a block diagram thereof. In this circuit diagram, an input signal 1 is input to an adder 2, an output of the adder 2 is input to a quantizer 4 through an integrator 3, and an output of the quantizer 4 is output to a gate driver circuit 6. The output of the gate driver circuit 6 is supplied to the power switch element 7. The output of the gate driver circuit 6 has a path fed back to the adder 2 through the attenuator 19.
[0027]
Compared with the conventional method in which the output of the quantizer 4 is fed back to the adder 4, the output of the gate driver circuit 6 for performing voltage amplification and current amplification sufficient to drive the power switch element 7 is directly fed back as in the present invention. However, the distortion is reduced and the linearity of the DC transmission characteristics is improved. FIG. 4 shows this DC transmission characteristic.
[0028]
FIG. 8 shows an embodiment in which the present invention is applied to a ΔΣ modulation step-down chopper. The voltage output to the load is compared with the reference voltage 17 to amplify the differential voltage, a signal obtained by modulating the differential voltage by the ΔΣ modulator 5 is output to the gate driver circuit 6, and the power switch element 7 is driven by the gate drive signal. In addition, the ΔΣ modulator 5 is fed back.
[0029]
The power supply input is an analog signal. For example, when a DC voltage is input, the output of the power switch element 7 can obtain a DC voltage with power amplification. That is, it can be driven as a switching power supply corresponding to the output voltage. Since the modulated signal is binarized, it is easy to configure as an integrated circuit, and a small switching power supply can be provided.
[0030]
In this way, by feeding back the output of the gate driver circuit 6 having sufficient current and voltage capacity to drive the power switch element 7 to the ΔΣ modulator 5, the gate driver circuit 6 greatly affects the input signal. The generated distortion can be reduced, and as shown in FIG. 9, the phase margin is large even when the power switch element 7 is switched at a high frequency, and the control can be stabilized.
[0031]
Although FIG. 8 particularly describes the step-down chopper, it is apparent that the same method can be used for a step-up chopper and a polarity inversion chopper.
[0032]
The switching signal generator according to claim 2 has at least one integrator 3 connected to the output of the adder 2, has a quantizer 4 connected to the output of at least one integrator 3, and performs ΔΣ modulation. Realize.
[0033]
Furthermore, the former improves sampling accuracy by providing two or more integrators 3 connected in series to the output of the adder 2 or two or more integrators 3 connected in parallel to the output of the adder 2. The latter can have outputs in parallel, and can provide a high-accuracy, multi-output switching power supply for a miniaturized integrated circuit.
[0034]
The switching signal generator according to claim 3 is a switching signal generator characterized by having a feedback path from the output of the gate driver circuit 6 connected to the output of the quantizer 4 to the input of the adder 2. This is necessary to correct the distortion generated in the circuit 6.
[0035]
The switching signal generator according to claim 4 is a switching signal generator having a gate driver circuit 6 for supplying a voltage and a current sufficient to drive the power switch element 7 and an output of the quantizer 4. Then, a sufficient output for driving the power switch element 7 cannot be obtained, and a signal to be fed back is necessary in order to exhibit a sufficient effect.
[0036]
The switching signal generator according to claim 5 is a switching signal generator having an attenuator 19 in a feedback path from the output of the gate driver circuit 6 to the input of the adder 2, and has a large amplitude from the gate driver circuit 6. The pulse signal is required to adapt to the ΔΣ modulator 5 input signal level, and the signal to be fed back is sufficiently effective.
[0037]
【The invention's effect】
In a switching power supply using the ΔΣ modulator 5, by feeding back the output of the gate driver circuit 6 to the ΔΣ modulator 5, distortion in the gate driver circuit 6 can be reduced and the power switch element 7 can be driven. The phase margin increases and control is stabilized. In particular, it is difficult to oscillate at a high switching frequency, and stable control can be provided. That is, it is possible to provide a switching power supply that hardly oscillates even at a high switching frequency and supplies an output voltage corresponding to the input voltage.
[0038]
Furthermore, since it is not easily affected by the noise of the power switch element output, especially when the power output is low, there is little switching loss, and a highly efficient switching power supply can be supplied.
[0039]
[Brief description of the drawings]
FIG. 1 is a block diagram of an example showing an embodiment of the present invention.
FIG. 2 is a block diagram using a conventional PWM modulator.
FIG. 3 is a block diagram of a conventional ΔΣ modulator.
FIG. 4 is a DC transmission characteristic diagram comparing the feedback of the gate driver circuit output of the present invention and the quantizer output feedback of the conventional method.
FIG. 5 is a block diagram using a conventional ΔΣ modulator.
FIG. 6 is a block diagram in which a conventional PWM modulator is applied to a step-down chopper power supply.
FIG. 7 is a block diagram in which a conventional ΔΣ modulator is applied to a step-down chopper power supply.
FIG. 8 shows an embodiment of a ΔΣ modulation step-down chopper according to the present invention.
FIG. 9 is a Bode diagram showing gain (GAIN) and phase (PHASE).
[Explanation of symbols]
1.Input signal
2.Adder
3. Integrator
4.Quantizer
5.ΔΣ modulator
6.Gate driver circuit
7.Power switch element
8.Output
9. Feedback
10. Frequency signal
11.Error amplifier
12.Diode
13.Capacitor
14.Inductance
15.Load
16.Resistance
17. Reference voltage
18.PWM (pulse width modulation) oscillator
19.Attenuator

Claims (5)

In a switching power supply that performs ΔΣ modulation on an analog signal or multi-bit digital signal and switches in response to the modulation signal, a gate driver circuit for a power switch element switching signal is provided, and the gate driver output is fed back to the ΔΣ modulator. A switching signal generator. In the switching signal generator of claim 1, wherein the ΔΣ modulator is an input signal and an analog signal or a multi-bit digital signals, having at least one integrator and the at least one adder, the output of the adder integration A switching signal generator, wherein at least one of the integrator outputs is connected to a quantizer input. In the switching signal generator of claim 1 or 2, the switching signal generator, characterized by having a path of at least one adder the feedback to the input of the ΔΣ modulator from the output of the gate driver circuit. The switching signal generator according to any one of claims 1 to 3 , wherein the gate driver circuit receives a quantizer output signal and is one of voltage amplification and current amplification sufficient to drive a power switch element. Alternatively, a switching signal generator characterized by performing both voltage amplification and current amplification sufficient to drive the power switch element. In the switching signal generator according to any one of claims 1 to 4, the path of the feedback, characterized in that it includes an attenuator to adapt the large amplitude pulse signal of the gate driver circuit ΔΣ modulator input signal level A switching signal generator.

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